/Engine/Source/Runtime/AnimGraphRuntime/Public/SequencePlayerLibrary.h
Set the start position of the sequence player. If this is called from On Become Relevant or On Initial Update then it should be accompanied by a call to SetAccumulatedTime to achieve the desired effect of resetting the play time of a sequence player.
static [FSequencePlayerReference](API\Runtime\AnimGraphRuntime\FSequencePlayerReference) SetStartPosition ( const [FSequencePlayerReference](API\Runtime\AnimGraphRuntime\FSequencePlayerReference) & SequencePlayer, float StartPosition )